The automated and precise location of non-bulk resource and components (e.g. engineered components, military supplies, cars, or general inventory items) in large, rough, or frequently unpredictable scenarios (such as those of civil engineering projects, war zones, car distribution, inventory management, etc.) is a challenging problem. In such scenarios, it is fundamental to be capable of exactly locating the components, so the right component is available for use by downstream processes at the right time and right place. For instance, the inability to locate a bolting tool or a pre-fabricated component required for installation on a project site have been observed to leave crane equipment and crews idle for several hours or even a full day. Similarly, the inability to locate a car in a common inventory and distribution yard also requires multiple hours, sometimes days, by crews. There is a need to properly and efficiently locate non-bulk resources or components over small or large areas (sometimes tens or hundreds of acres) in unpredictable, non-controlled, or dynamic scenarios.
Traditional manual tracking of resources and components tends to be time consuming, error prone, and inefficient. The solution needs an adequate blending of advanced technologies and reasoning mechanisms to facilitate the location of multiple, even thousands, resources/components over extensive areas in short amounts of time and at inexpensive costs. Battery-less identification marking technologies are characterized by the data communication between a powered transmitter/receiver unit (also referred as transmitter, receiver, or reader) and a battery-less electronic identification device (typically referred as tag) through electromagnetic energy waves (e.g. radio waves). An example of such battery-less identification marking technologies is passive radio frequency identification (RFID).
Passive tags, as an example of battery-less identification marking technologies, operate without a battery source and offer low costs and interoperable communications with transmitters/readers, even though their technical limitations, such as a short range of communication from the tag to the reader (i.e. short read range or communication range). The lack of battery is indeed at the core of low passive tag costs. Passive RFID tags are, in essence, a coiled antenna connected to a circuit. The passive RFID tags make use of the magnetic energy of the incoming signal from the receiver to power a signal back to the receiver. FIG. 1 shows a typical communication of RFID receiver and tag. The battery-free characteristic of passive tags results in unit costs that range from a few cents to a few dollars. These unit costs are several orders of magnitude less than those of active (battery-powered) tags. This same battery-free characteristic also enables the physical design of tags in a large variety of shapes and sizes. For example, passive tags vary from flexible (similar to barcodes) to solid or encapsulated (similar to active tags). In addition to their low costs, the EPC UHF Generation 2 (or equivalent) standard guarantees the interoperability of passive tag and reader products. Virtually all passive products in the market are EPC UHF Generation 2 (or equivalent) compliant and hence interoperable. Thus, regardless of the manufacturer, the signal of any passive tag can be read and decoded by any reader and vice versa.
Despite the low costs and interoperability characteristics of passive RFID technologies, the need to keep passive tags and readers in very close proximity has historically limited their applicability. Indeed, a passive tag only emits in response to the reader signal (as opposed to active tags that continually emit beacon signals) and actually obtains its power from that signal. The reader signal is captured by the inductive coil antenna, which, at the same time, energizes the tag and supplies the power to respond back to the reader. Thus, passive tags emit weak signals and hence can only communicate with the reader if this is within a short communication range.
An automated and mobile identification and localization infrastructureless approach with a combination of active (battery assisted) RFID technologies and range-based algorithms is known. Even though the evident cost benefits of such, the actual upfront cost of active RFID tags (starting at $30 per unit) tremendously limits its actual application. Consumers of such approaches (contractors, defense, inventory management, supply chain, etc.) need to tag hundreds of thousands of items, each of them with a costly tag. In addition, in the previous approach, the antenna and receiver were placed in a mobile roving unit that must be able to circulate nearby the tagged components, so it can collect multiple unique signals for each tag, at the same time it collects the GPS position of the rover. Such ability to circulate close to any tagged component is often not possible at the expense of inaccurate location results. The aim of this previous active-RFID and mobile approach is to generate a unique location estimate (assumed as a stationary or non-moving condition) for all the tagged components with batch or discrete data collection efforts, i.e. without a real-time component. With this approach and given the (often) long physical distances between reader(s) and tags during the data collection in combination with the presence of obstacles and other signal attenuation issues affecting the signals traveling between distant reader(s) and tags, and even more when the components are spread in large areas and hence data collection efforts by roving units are minimized, there is no guarantee that a location can be estimated for all the tagged components, or that such location(s) can be accurate. Thus, the location of certain components is often lost and hence such components cannot be tracked. In any case, all that can be initially known from a tagged component is that it lies somewhere around the rover position in a radius equivalent to the communication range of the active radio frequency devices, typically in the range of hundreds to thousands of feet.
Corresponding reference characters indicate corresponding elements among the view of the drawings. The headings used in the figures do not limit the scope of the claims.